<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>尺寸</title>
    <style>
        p.ex
        {
            height:100px;
            width:100px;
            max-width:20%;
            min-height:100px;
            min-width:50px;
        }
        html {height:100%;}
        body {height:100%;}
        img.normal {height:auto;
            max-height:200px;
        }
        img.big {height:50%;}
        img.small {height:10%;}
    </style>
</head>
<body>
<p class="ex">这个段落的高和宽是 100px.</p>


</body>
</html>